Truck-drawn trailers equipped with refrigeration units require a high degree of reliability, as is discussed in our U.S. Pat. No. 4,187,093. In said patent there is disclosed a novel and improved solid state temperature control and malfunction signal apparatus utilizing a voltage divider to establish a plurality of temperature reference points and this voltage divider operates independently of the temperature sensor. The circuit shown and described therein is particularly effective for detecting and producing a warning signal to prevent an overheat situation to prevent damage to the cargo due to overheating.
In temperature controls for trailer-equipped refrigeration units it is important to operate the unit within a desired temperature range. In the event the cooling unit should stick and continue to cool below a desired temperature, there would be necessary energy expended and in some instances this may cause damage to certain types of cargo, making it desirable to detect an overcool malfunction. To this end, in accordance with the present invention there is provided a novel and improved temperature control circuit that will detect and signal overcooling malfunction, preferably using the same signal device for signaling either an overheat or an overcool malfunction situation.